In known forms of lever-operated grease guns as disclosed, for example, in the U.S. Pat. Nos. 2,923,443, 2,941,854, and 3,780,830 it is a prevalent practice to weld a square cross-section pump cylinder diametrically across the exterior of the end wall of the head cap and to provide a transverse pivot pin at the closed end of the pump cylinder for a pair of links of the pump-operating lever. When high pressure is applied on the grease by the pump piston, the resulting large tensile forces applied on the aforesaid links tends to break the pump cylinder away from the end wall of the head cap. It has been proposed as in U.S. Pat. No. 3,627,178 to make a portion of the pump cylinder of round bar stock but in that case the end wall of the head cap is formed with axial projections which provide a concave cylindrical seat in which the round portion of the pump cylinder is welded.
In the grease guns according to U.S. Pat. Nos. 2,923,443, 2,941,854 and 3,780,830, a check valve body is screwed into a lateral opening in the pump cylinder adjacent the closed end of the cylinder, the dispensing tube of the grease gun being screwed into the check valve body.
It has been proposed by U.S. Pat. No. 3,291,350 to mount the pump cylinder of a grease gun in diametrically opposite openings through the side wall of the head cap but in that case the outlet check valve is coaxially aligned with the cylinder bore and the link pivot integrally projects from the end wall of the head cap.